AN OVERVIEW OF CHEMICAL FATE AND TRANSPORT MODELING IN THE VADOSE ZONE: Overview of terrestrial process and modeling / A. S. Donigian, Jr., and P. S. C. Rao -- Transport mechanisims and loss pathways for chemicals in soils / W. A. Jury and R. L. Valentine -- Generic steps in the field validation of Vadose zone fate and transport models / S. C. Hern, S. M. Melancon, and J. E. Pollard -- Example field testing of soil fate and transport model / PRZM, Dougherty Plain, Georgia, K. F. Hedden -- Eample models testing studies / A. S. Donigian Jr and P.S.C. Rao -- CHEMICAL PROCESSES, PARAMETER ESTIMATION, AND VARIABILITY IN THE VADOSE ZONE: Chemical movement through soil / W. A. Jury -- Volatilization from soil / W. A. Jury -- Adsorbtion of organic chemicals into soil / W. A. Jury -- Biotransformation / R. L. Valentine and J. L. Schnoor -- Nonbiological transformation / R. L. Valentine -- Spatial variability of soil properties / W.A. Jury.